title: Effects of a delocalizable cation on the headgroup of gemini lipids on the lipoplex-type nanoaggregates directly formed from plasmid DNA.
abstract: Lipoplex-type nanoaggregates prepared from pEGFP-C3 plasmid DNA (pDNA) and mixed liposomes, with a gemini cationic lipid (CL) [1,2-bis(hexadecyl imidazolium) alkanes], referred as (C16Im)2Cn (where Cn is the alkane spacer length, n = 2, 3, 5, or 12, between the imidazolium heads) and DOPE zwitterionic lipid, have been analyzed by zeta potential, gel electrophoresis, SAXS, cryo-TEM, fluorescence anisotropy, transfection efficiency, fluorescence confocal microscopy, and cell viability/cytotoxicity experiments to establish a structure-biological activity relationship. The study, carried out at several mixed liposome compositions, α, and effective charge ratios, ρeff, of the lipoplex, demonstrates that the transfection of pDNA using CLs initially requires the determination of the effective charge of both. The electrochemical study confirms that CLs with a delocalizable positive charge in their headgroups yield an effective positive charge that is 90% of their expected nominal one, while pDNA is compacted yielding an effective negative charge which is only 10-25% than that of the linear DNA. SAXS diffractograms show that lipoplexes formed by CLs with shorter spacer (n = 2, 3, or 5) present three lamellar structures, two of them in coexistence, while those formed by CL with longest spacer (n = 12) present two additional inverted hexagonal structures. Cryo-TEM micrographs show nanoaggregates with two multilamellar structures, a cluster-type (at low α value) and a fingerprint-type, that coexist with the cluster-type at moderate α composition. The optimized transfection efficiency (TE) of pDNA, in HEK293T, HeLa, and H1299 cells was higher using lipoplexes containing gemini CLs with shorter spacers at low α value. Each lipid formulation did not show any significant levels of toxicity, the reported lipoplexes being adequate DNA vectors for gene therapy and considerably better than both Lipofectamine 2000 and CLs of the 1,2-bis(hexadecyl ammnoniun) alkane series, recently reported.
authors.affiliation: Departments of ‡Organic Chemistry and ⊥Molecular Reproduction Development and Genetics, Indian Institute of Science , 560012 Bangalore, India.
authors.forename: Santosh K
authors.initials: SK
authors.lastname: Misra
authors.forename: Mónica
authors.initials: M
authors.lastname: Muñoz-Úbeda
authors.forename: Sougata
authors.initials: S
authors.lastname: Datta
authors.forename: Ana L
authors.initials: AL
authors.lastname: Barrán-Berdón
authors.forename: Clara
authors.initials: C
authors.lastname: Aicart-Ramos
authors.forename: Pablo
authors.initials: P
authors.lastname: Castro-Hartmann
authors.forename: Paturu
authors.initials: P
authors.lastname: Kondaiah
authors.forename: Elena
authors.initials: E
authors.lastname: Junquera
authors.forename: Santanu
authors.initials: S
authors.lastname: Bhattacharya
authors.forename: Emilio
authors.initials: E
authors.lastname: Aicart
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry; D002412:Cations / Q000737:chemistry; D002460:Cell Line; D004247:DNA / Q000737:chemistry*; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D008055:Lipids / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry; D015394:Molecular Structure; D049329:Nanostructures / Q000737:chemistry*; D010316:Particle Size; D010957:Plasmids; D013499:Surface Properties
chemical_list: D001672:Biocompatible Materials; D002412:Cations; D008055:Lipids; D008081:Liposomes; D004247:DNA